1. Technical Field
The present disclosure relates generally to a method and system for calibrating the voltage of a battery pack.
2. Discussion of Technical Background
A battery pack usually includes a plurality of cells connected in series for supplying electric power to electronic equipment, such as an electronic vehicle, portable computer, electronic camera, or the like. The battery pack is usually equipped with a voltage detection apparatus that detects the voltage of each cell for capacity calculation and protection of each cell. The detected cell voltage level may be a floating voltage, which is measured by taking across the positive and negative terminals of each battery cell. In some cases, it may be desirable to translate the floating cell voltage to a ground referenced voltage so that a ground-based A/D converter (ADC) can be used to measure the translated voltage accurately.
One conventional approach to translating the floating cell voltage to a ground referenced voltage utilizes a differential operational amplifier with four externally coupled resistors. However, for battery packs having two or more battery cells connected in series, this conventional approach requires the use of a high voltage operational amplifier to accommodate the relatively large potential difference between the inputs of the operational amplifier. A high voltage operational amplifier may have a supply voltage between about 10 volts and 40 volts and may have a larger common-mode gain and offset voltage errors compared with a low voltage operational amplifier having a supply voltage less than or equal to about 5 volts. These errors may then need to be corrected by balancing all four resistor values in a complex calibration process that may require making fine adjustments to at least one of the four resistors. Otherwise, since the offset voltage errors are related to common-mode voltages, all the cell terminals should be connected to a battery management system (BMS) in a given order for accurate voltage measure. However, it would raise the special requirement for the BMS assembly, which may increase the cost and bring the inconvenience to the customs.
Accordingly, there exists a need to provide an improved method and system for calibrating the voltage of the battery pack, which reduces voltage translation error and simplifies calibration process.